The seasonally adjusted sales rate for August accelerated to 14.53 million from 14.1 million in July and 12.5 million a year earlier. The results topped most analysts' forecasts and marked the highest SAAR since the U.S.-sponsored cash-for-clunkers program in August 2009.

U.S. new car and light-truck sales have advanced 15 percent to 9.7 million this year through August and remain a bright spot amid mixed economic signals and lackluster job growth.

"The auto industry continued to outperform the general economy in August," Bill Fay, Toyota group vice president and general manager, said in a statement. The company posted a 46 percent sales increase last month as it continued its recovery from an earthquake-hampered 2011.

Honda Motor Co. reported a 60 percent increase from a year earlier, when it also suffered from quake-related inventory shortages. Volume at the Honda brand jumped 58 percent to 115,675 units; Acura deliveries climbed 73 percent to 15,646 units.

Among major brands, VW led the way with a 63 percent jump, its 12th straight month of gains of at least 25 percent. Including Audi, up 13 percent, and other luxury brands, VW Group sales jumped 48 percent.

"Our Iron Man streak continued last month," Reid Bigland, head of the Dodge brand and U.S. sales operations for Chrysler, said in a statement. "An incredibly resilient U.S. new vehicle sales industry doesn't hurt."

TrueCar.com estimates industry incentives averaged $2,457 last month, down 2 percent from July and off 6 percent from August 2011. Chrysler, GM and Nissan offered some of the biggest deals in August, while Hyundai, Toyota, and Honda were less generous with discounts, TrueCar said.